With improvement of wireless communication techniques, a wireless device may have various components belonging to different wireless communication systems. For example, a wireless local network gateway product comprises a wireless access point (AP, Access Point) device and a station (Station) device, wherein the AP device is responsible for providing wireless access signal coverage within a certain area, and various terminal devices (for example, a computer, a cell phone, etc.) in the coverage of the AP device may access a network via the station device or the AP device.
Traditional AP devices access the Internet (INTERNET) on uplink via Ethernet or fiber optics in order to acquire enough bandwidth. However, with improvement of wireless techniques, High Speed Packages Access (HSPA, High Speed Packages Access) technique, Worldwide Interoperability for Microwave Access (WiMAX, Worldwide Interoperability for Microwave Access) or other wireless communication standards, instead of the Ethernet or fiber optics, have been used by the traditional AP devices (i.e., wireless gateway product) for uplink. Thus, the mobility and portability of the access points are greatly improved, which, however, directly results in simultaneous operating in a small space of both a wireless local area device communicating via Wireless Fidelity (WIFI, Wireless Fidelity) technique and other communication systems. Said other communication systems can be any one of Universal Mobile Telecommunications System (UMTS, Universal Mobile Telecommunications System), Global System for Mobile Communications (GSM, Global System for Mobile Communications), Code Division Multiple Access (CDMA, Code Division Multiple Access) system, Worldwide Interoperability for Microwave Access (WiMAX, Worldwide Interoperability for Microwave Access), Time Division-Synchronous Code Division Multiple Access (TD-SCDMA, Time Division-Synchronous Code Division Multiple Access) system, etc.
In those systems, in order to gain optimal coverage, the transmit power of the WIFI device is maintained to be highest all the time without control. Thus, the effect that a signal transmitted by the WIFI device brings into a signal received by terminals of other system must be taken into account when designing these terminals of other system. However, since the two communication systems co-exist in a small device, the isolation of the antennas between both systems is very low; and thus the other systems are easily blocked by high-power WIFI transmitting signals by the device. In order to prevent a sensitivity of the receiver from being degraded due to the blocking, the power of a WIFI transmitting signal arriving at the receiver must be restrained below a specific power.
In the prior art, a filter is added onto the receiving path of the other communication systems, or the restraint requirements of the filter on the frequency band of WIFI is enhanced.
During the study and practice on the prior art, the inventor of the present invention observes that: the enhancement of the restraint requirements of the WIFI filter on the first frequency band results in high difference loss within a normal receiving passband and thus results in deterioration of the system performance under normal conditions; meanwhile, the addition of the filter onto the receiving paths of the other communication systems or the enhancement of the restraint requirements of the filter results in the increase of the cost of the device.